Definition of Pyloric stenosis:

Pyloric stenosis is a narrowing of the pylorus, the opening from the stomach into the small intestine.

Causes, incidence, and risk factors:

Pyloric stenosis is caused by a thickening of the muscles of the pylorus. This thickening prevents the stomach from emptying into the small intestine.

The cause of the thickening is unknown, although genetic factors may play a role. Pyloric stenosis occurs more commonly in boys than in girls, and is rare in patients older than 6 months. The condition is usually diagnosed by the time a child is 6 months old.